Superheater



Oct. 2, 1934. H, RTMANN 1,975,508

SUPERHEATER Filed Sept. 10, 1932 INVENTOR BY Q/ZQ ATTORNEY Patented Oct. 2, 1934 SU PERHEATER OttoH. Hartmann, Cassel-Wilhelmshohe, Germany, assignor to The superheater Company;

Application September 10,1932, Serial No. 632,507 In Germany September 16, 1931 claim. (01.122- -462) 'The invention relates to flue superheaters, particularly those used in locomotive, locomobile and marine boilers in which the superheater loops extend into the fire box or return chamber in order to obtain higher superheat. It is old in the prior art to extend superheater loops into a return chamber without providing any protection. In some cases of this kind the heating gases are tempered or cooled by bringing them into contact with water tubes before they touch the superheater loops. It is further old in locomotive boilers to equip the loops extending into the fire box with protective members slipped on them, such members having the shape of shields open on the upper side except for the closed end which covers the extremity of the return bend. On their under side they may be closed or may have a slit in line with the space between the two branches of the superheater element. In the case of the unprotected return bends the entire surface is utilized for heat absorption but a protection against damage by the intense flames is either entirely absent or in case water tubes are interposed, such protection is present only to a certain degree. In the second instance such protection is provided, but a portion of the surface of the return bends is removed from the immediate action of the heating gases, so that something less than the entire surface of the return bends is used as heat exchange surface and touched by the gases.

Contrasted with this prior practice, protection of the return bends extending into the fire box against the intense flames is provided by the present invention while at the same time the entire surface is utilized and in addition the heat exchange is considerably raised and the total heat absorption increased. This is accomplished by extending into the fire box or return chamber not only the return bends of the superheater loops but also the flues. For this purpose the length of the flues is either directly increased by an amount corresponding to the portion of the superheater loops extending into the fire chamber so that the flues are rolled or expanded into the flue sheet not at their ends but at a point spaced from the ends, or the prolongation of the flues may be efiected by means of open-ended thimbles or tube lengths which are welded to the ends of the flues or to the flue sheet or which may have their ends inserted into the flues and which are secured in position by welding, soldering, rolling or screwing into place. The return bends and the extended ends of the flues may be made of special heat resisting steel or of ordinary steel which has been rendered heat resistant by calorizing or parkerizing. Utilizing the present invention in connection with such steels, a superheater may have its ends extended into a fire box chamber where the temperature may be as n high as 1200 C. The special advantage of the invention is found in the fact that a relatively higher superheat can be obtained with it than with return bends extending into the flre box directly without protection. The reason for this {165 is that the portions of the return bends extending into this highest temperature zone are surrounded by a flue just as the remaining portion of the element, such portion of the flue within the fire box further not being surrounded by water, and that the gases flowing through theseportions move with a velocity comparable to that of the gas flow over the remaining portion of the elements. This is not true in the case where the return bends extend into the fire box without any protection. :15 This high velocity of course results in a higher rate of heat transfer.

The drawing shows some illustrative examples.

In them, Fig. 1 is a longitudinal section through a fire box and the adjacent portions of the flues of a locomotive boiler; Fig. 2 is a similar section through the return chamber of a marine boiler; Figs. 3 and 4 are respectively a longitudinal section and fragmentary front view of the fiue sheet of a varied form of the invention; and Fig. 5 is 2.x section similar to that of Fig. 4 of a further variation.

In Fig. 1 reference numeral 1 designates the fire box or combustion chamber, 2 designates the flue sheet and 3 the flues. The superheater loops 4190 extend in known manner beyond the sheet 2 into the fire box, all of them in the form illustrated extending the same distance, while the flues 3 are in accordance with the invention also extended a corresponding distance into the fire box. Prefer-- ably the flues are slightly flared at their ends.

In Fig. 2, 6 is the combustion chamber or return chamber of a marine boiler into which the return bends 4 of the superheater loops extend in a known manner, the distances by which they1i100 so extend being in this case graduated. The corresponding extensions of the flues 7 are produced by welding the open-ended thimbles or flue lengths 8 to the flues 7 which extend slightly beyond the flue sheet 9, such welding being doneif for example electrically.

In Fig. 3, 10 designates the flue sheet, 11, the flues and 12, the return bends 0f the superheater loops extending into the chamber. The exten sion thimbles 14 are somewhat enlarged at one;

end and are welded not to the fiues 11 but are secured to the flue sheet 10 by spot welding as at points 15 indicated in Fig. 4.

In Fig. 5 is shown a form in which the extension thimbles 16 are inserted into the ends of the fines 11. They are advantageously provided with a spacing shoulder 17 and secured in position by spot welding as at 18. The portion of the thimble extending into the flue in this case has the same beneficial effect in addition as thimbles which are at times inserted into the flues to protect them at these points. i

It will be understood that the forms shown are only illustrative. The essence of the invention consists in having the return bends of the superheater loops which extend into the fire box or return chamber lie inside of extensionsof the flues which on the one hand protect them against direct impingement of the flame, and on the other hand permit their entire heating surface to come into contact with gases flowing through them with increased velocity without heat being abfines extending into the gas chamber at the inlet of the fiues for a distance at least twice as great as the diameter of the fines, the extensions being made of material of greater heat resisting property than the fiues themselves, tubular superheater elements in the fiues with portions extending into the flue extensions, whereby the heat transfer is increased but direct flame impingement against the sides of the portions in the extensions is prevented.

H OTTO H. HARTMANN. 

